Regenerative refrigeration system with means for controlling compressor discharge



Sept. 2, 1969 KRAMER 3,464,226

REGENERATIVE REFRIGERATION SYSTEM WITH MEANS FOR CONTROLLING COMPRESSORDISCHARGE Filed Feb. 5, '1968 2 Sheets-Sheet l INVENTOR ATTORNEYS Sept.2, 1969 D. E. KRAMER 3,464,226

liEGEJNEHA'llVIfi REFRIGERATION SYSTEM Wl'IH MEANS FOR CONTROLLINGCOMPRESSOR DISCHARGE Filed Feb. 5, 1968 2 Sheets-Sheet 2 BYmm)2 VATTORNEYS United States Patent Jersey Filed Feb. 5, 1968, Ser. No.702,903 Int. Cl. F25b 41/00, 47/00 US. Cl. 62196 Claims ABSTRACT OF THEDISCLOSURE A regenerative refrigeration system having, as usual, asingle compressor and condenser with a plurality of evaporators,arranged for the defrosting of one evaporator at a time while the otheror others is or are active, and the feeding of the condensate from theevaporator being defrosted into the refrigerant supply conduit leadingto the thermostatic valve or valves of the other or others, the systemincluding means for automatically temporarily increasing the pressure ofcompressor discharge during defrosting to expedite the latter. In placeof the single compressor there may be employed a condensing unit havinga plurality of compressors constructed with a common suction conduit anda common discharge to a single condenser, e.g. US. Patent No. 3,140,041,dated July 7, 1964.

FIELD OF THE INVENTION The present invention comprehends the provisionof a regenerative refrigeration system comprising the usual members thatis particularly fitted for installations in which the condenser islocated in a substantially elevated position as compared with theplurality of evaporators, which may be instanced by the common practiceof supermarkets and the like, where it is convenient to have thecondenser on the roof of the building while the evaporators are On theground or service floor usually in the show cases for chilled food.

As is well known to the refrigeration profession, in these regenerativesystems the condensed refrigerant flowing from the evaporator that isbeing defrosted is fed into the supply conduit that leads to thethermostatic valves associated with the active evaporators. Thus thedesired expedition of defrosting of each evaporator in turn depends notonly upon the amount of heat from the compressor but importantly uponthe difference in pressure between the compressor discharge and thepressure in the liquid refrigerant supply conduit for the activeevaporators.

In this latter respect difiiculty has been encountered when thecondenser is elevated, due to the pressure of the column of condensedrefrigerant in the long conduit leading downward to the usual receiverwhich increases the pressure in the refrigerant supply conduit for theactive evaporators, with consequent slowing of the defrosting of theevaporator that is undergoing this step.

The present invention surmounts this difiiculty by providing automaticmeans for temporarily increasing the pressure of the compressordischarge during each period of defrosting, thus counterbalancing theabove described 3,464,226 Patented Sept. 2, 1969 increase of pressure inthe supply conduit and shortening the defrosting periods. The pressureof the discharge is returned to normal between defrosting periods.

BRIEF DESCRIPTION OF THE DRAWING A practical embodiment of the inventionis depicted in the accompanying drawing in which:

FIG. 1 represents diagrammatically a regenerative sys- =tem comprisingthree evaporators, one being defrosted and the others active. Thecondenser is located on the roof of a building (e.g. supermarket) whilethe receiver may be on the lower sales service level where therefrigerated open show cases are also located, and which con tain thefrozen food for sale and also house the refrigerating evaporators;

FIG. 2 represents diagrammatically the means of this invention fortemporarily increasing the pressure of the compressor discharge inoperative association with a valve which controls discharge pressure;

FIG. 3 represents diagrammatically a detached modification of the meansof FIG. 2; and

FIG. 4 represents diagrammatically a timing control means fordefrosting.

In these regenerative systems, which are rapidly increasing in useespecially for commercial establishments such as supermarkets and thelike, it is quite desirable to have several separate evaporatorspositioned within service or sales fixtures, e.g. food show cases, alloperated by a single compressor, condenser and receiver (or condensingunit above described), but each with its own thermostatic expansionvalve or the equivalent, all of which are fed by a single refrigerantsupply conduit from the condenser and receiver. Of course, theevaporators must be defrosted at intervals and a primary considerationresides in the fact that the defrosting be not only thorough, but swiftin order to avoid spoiling the food within the show case where theevaporator is being defrosted.

The speed of defrosting depends on the quantity of hot. gas from thecompressor discharge, and greatly on the difference of pressure betweenthe hot gas stream and the pressure in the above mentioned common liquidrefrig erant supply conduit for the expansion valves of the evaporatorsbecause the condensate from the evaporator that is being defrosteddrains into said supply conduit and relative increase of pressure in thelatter resists the drainage and slows the defrosting by delaying theexposure of the inner surface of the evaporator undergoing defrost tothe hot gas.

It will thus be clear that, when the condenser is substantially elevatedwith respect to the liquid refrigerant supply conduit leading to theexpansion valves of the evaporators, the pressure of the column ofcondensate in the vertical conduit from condenser to said supply conduitwill directly increase the pressure in the latter, which increase hasbeen found to be as much as 15-20 psi, and seriously prolong thedefrosting step.

This problem has been solved by applicant through the incorporation inthe system of pilot means for, at the period of each defrosting,automatically temporarily increasing the pressure of the compressor hotgas discharge by action upon the inlet controlled pressure valve whichcommonly governs compressor discharge, so as to counterbalance the abovedescribed increase of pressure in the supply conduit for the activeevaporators.

Turning now to the drawing and referring to FIG. 1 that represents awhole regenerative system, there are three evaporators 1, 2 and 3, eachpositioned within its own fixture 4, 5 and 6, respectively, which latterare indicated in broken lines and may be assumed to be frozen food casessuitably located. Each evaporator is fitted with its own thermostaticexpansion valve 7, 8 and 9, for the usual function; and with checkvalves 10, 11, 12 in pipes that by-pass the expansion valves and permitdrainage of condensate during defrosting.

The compressor is denoted by 13; the condenser by 14; the receiver by15; and the liquid supply line to the expansion valves by 16. The hotgas conduit from compressor to evaporators is marked 17 while thesuction conduit leading back to the compressor has been given thereference numeral 18. Three-way solenoid valves 19, 20 and 21,respectively, serve for opening and closing communication of theevaporators with the hot gas conduit or the suction conduit according tothe state of operation of the system, as will be described.

An inlet pressure regulating valve 22 controls the pressure of thecompressor discharge while an outlet pressure regulating valve 23controls the pressure in the receiver 15 and supply conduit 16regardless of the setting of valve 22. In addition, a check valve 24permits flow of condensate from condenser 14 to receiver 15 but preventsreverse flow. This is a known arrangement which is shown e.g. in FIG. 2of US. patent to W. Micai and the present inventor, No. 2,934,911, datedMay 3, 1960. Arrows indicate the direction of flow in the dischargeconduit 17 and suction conduit 18.

The inlet pressure regulating valve 22 that controls compressordischarge pressure is well known to the profession in structure andfunction which is thought to dispense with anything more than a briefdescriptive outline of its features that are pertinent to the presentinvention though not strictly a part thereof.

It should be noted that, while FIG. 1 shows the compressor, condenserand receiver as scattered, there may be substituted a condensing unit,above mentioned, in which the compressor, condenser and receiver aremounted on one platform, and further, that the compressor and receivermay be located indoors while the condenser is outdoors to have plenty ofair, e.g., on the roof.

FIG. 2 illustrates the foregoing and the operative association of thisinvention therewith. This valve, of course, is formed with an inlet 25and outlet 26 and there is a closure element 27 which establishes theextent to which the inlet and outlet are in communication and, hence,the setting of the valve in respect to control of compressor dischargepressure. This element is arranged for vertical movement and is urgedupwardly toward a closed position by a spring 28. However, the movementof element 27 is governed by a piston 29 within a cylinder 30 which isformed with a port 31 in its head 32; and the piston is controlled by adiaphragm 33 which overlies the port 31 and, in turn, is under theinfluence of a spring 34, the effectiveness of which depends on thepressure under the diaphragm.

The result of the foregoing is that lessening of the pressure under thediaphragm will, according to its degree, permit movement of the element27 toward a closed position and thus increase the inlet pressure settingof the valve 22 that controls the pressure of discharge from thecompressor 13, this movement by the piston 29 being facilitated by asmall leak orifice 32' through its top. As above noted, the essentialconstruction and functioning of these inlet pressure controlled valvesare well known and understood by the refrigeration profession so thatthe foregoing is deemed adequate for an understanding of this inventionto be specifically described.

The substance of the invention involves an arrangement of pipes andvalves therein which provides a pilot control of the pressure beneaththe diaphragm 33, which arrangement is illustrated in FIG. 2 andcomprises the following: a pilot inlet manifold 35 is screwed into thecylinder head 32 and opens into the space between the latter and thediaphragm 33. The manifold is connected by a pipe 36 with a three-waysolenoid valve 37, which latter is in communication by another pipe 38with the main valve inlet 25. A third pipe 39 leads from valve 37 to theouter end of the manifold and incorporates a spring loaded check valve40 which permits flow to the manifold but prevents reverse flow. Theload on the spring of this valve may, for example, be 15 p.s.i.

Before proceeding to the operation of this assembly of pipes and valves,it seems advisable to explain that the whole matter of defrosting theevaporators in sequence, raising the pressure of hot gas defrostingduring each period of defrosting and returning it to normaltherebetween, and feeding the condensate from each evaporator as it isbeing defrosted into the liquid refrigerant supply conduit leading tothe expansion valves of the active evaporators, may be controlled by anelectric clock system such as is commonly used with solenoid valves andwhich is well known to operators and engineers in this field. A typicalclock wiring diagram is shown in FIG. 4, the unit being designed to turnon and off the valves controlling defrosting of a single evaporator, andas many timing units being provided as there are evaporators. Byproviding separate clocks, the hour and duration of each defrost cyclecan be set with regard for, but independently of, the hour and durationof all other evaporators, so that the evaporators may be sequentiallydefrosted according to the settings of their clocks. At the start ofeach defrost cycle the respective 4-way solenoid valve 19 or 20 or 21 isturned to close the connection to suction line 18 and establishconnection with hot gas line 17 (see valve 20 in FIG. 1), simultaneouslyopening 5-Way solenoid valve 37 (FIG. 2, or 2-way solenoid valve 41,FIG. 3) from hot gas discharge 25 to manifold 35. At the end of thedefrost cycle the valves are returned to refrigerating position.

Thus each defrosting step is timer initiated by the clock which may alsoterminate the defrost. The timer may be set to defrost, say, every one,two or three hours and to end the step when the period has expired, aswell as to determine the spacing of the defrost of the severalevaporators and the sequence of the same. The timer, of course, actsupon the several solenoid valves 19, 20 or 21.

It is also well known to terminate the defrosting steps by a thermostatsensing the temperature of a selected point on the suction conduit or ata selected point at the evaporator.

Assuming the present invention to be controlled entirely by a timer;when the time arrives for defrosting an evaporator, e.g. the onenumbered 2 in FIG. 1, its valve 20 is turned to the position shown inwhich communication is opened to the hot gas discharge conduit 17 andclosed to the suction conduit 18, while the pilot valve 37 is turned toclose pipe 36 and open pipe 39 which severs the open connection of thepilot inlet manifold with the main valve inlet 25 and establishesconnection of the manifold with the said inlet through the spring loadedcheck valve 40, thus lowering the pressure in the manifold and beneaththe diaphragm 33, which permits the piston 29 to move the closingelement 27 to a position that restricts the passage between the maininlet 25 and the main outlet 26 thereby increasing the pressure settingof the said valve, which is marked 22 in FIG. 1, and consequentlycorrespondingly increasing the pressure of the compressor discharge inthe hot gas conduit 17 now in open communication with the evaporator 2and defrosting the latter.

As the defrosting proceeds, the refrigerant condensed by the meltingfrost on the air side of the evaporator 2 drains through the check valve11 into the liquid supply conduit 16 which feeds the expansion valves 7and '9 of evaporators 1 and 3 that are active, and the increase ofpressure in the compressor discharge conduit 17, above explained,facilitates this drainage to speed the defrost.

At the expiration of the defrosting period according to the setting ofthe timer for the same, the valve 20 of evaporator 2, turns to closecommunication with discharge conduit 17 and open communication withsuction conduit 18 to cause evaporator 2 again to become active.

At the same time valve 37 turns to open pipe 36 which increases thepressure under diaphragm 33 and causes the piston 29 to move the closureelement 27 downwardly and enlarge the passage between inlet 25 andoutlet 26, thus reducing the pressure setting of the valve andsimultaneously reducing the pressure in discharge conduit 17; whichcondition obtains until the timer for the solenoid valves initiates thedefrosting of another evaporator, which step proceeds as described abovein reference to evaporator 2.

The modified form of the invention presented in FIG. 3, consists merelyin the substitution of a two-way solenoid valve, denoted by thereference numeral 41, for the three-way valve 37 of FIG. 2; and thesubstitution of an automatic outlet pressure regulating valve, marked42, for the check valve 40 of FIG. 2, the setting of valve 42corresponding to the setting of the spring in valve 40.

The operation of this modified form of the invention is the same asabove described in connection with FIG. 2, but the use of the two-wayvalve 41 is more economical than the three-way, and the adjustment ofthe outlet pressure valve 42 is simpler than the adjustment of thespring in check valve 40 due to the fact that the valve can beexternally adjusted for suitable magnitude of pressure reduction whilethe system is operating.

Although not shown in the drawing, as it is conventional, the water ofdefrost will be permitted to run off by pipe to any suitable disposalpoint, e.g., sewer.

It is thought that the foregoing adequately explains the value of thisinvention in connection with regenerative refrigeration systems,especially when the condenser is located in an elevated positionrelative to the evaporators, which has almost become a must in manycommercial structures; 'but I desire it to be understood that variouschanges may be made in the parts and their arrangement without departingfrom the scope of the invention; and hence, I do not intend to belimited to any detail shown in the drawing or described in thespecification, unless the same is recited in the claims or required bydisclosures of the prior art.

What I claim is:

1. In a regenerative refrigeration system having at least onecompressor, a condenser, a plurality of evaporators, a common hot gasdefrost conduit for the evaporators, a common suction conduit for theevaporators, a common liquid refrigerant supply conduit for theevaporators, means for defrosting the evaporators singly, means fordraining into the supply conduit the condensed refrigerant from eachevaporator as it is being defrosted, and an inlet pressure regulatingvalve for controlling the pressure of the hot gas compressor discharge;the improvement which comprises providing means between said compressorand condenser for automatically increasing the pressure of the hot gasdefrost discharge while an evaporator is being defrosted to acceleratethe drainage of the condensed liquid refrigerant therefrom into theliquid supply conduit to the evaporators.

-2. A system as defined in claim 1, in which the condenser is elevatedwith relation to the liquid supply conduit for the evaporators.

3. A system as defined in claim 1, in which the improvement alsoincludes means for automatically restoring the pressure of the hot gasdischarge to normal between the defrosting periods.

4. A system as defined in claim 1, in which the means for automaticallyincreasing the pressure of the hot gas discharge comprises a pilot valvemanifold operatively connected with the pressure regulating means of theinlet pressure regulating valve, a pipe connection from the saidmanifold to the inlet of the said valve, and a control valve in the saidconnection adapted to open and close the said connection.

5. A system as defined in claim 4, which also includes a second pipeconnection between the manifold and the inlet of the pressure regulatingvalve, which second con nection contains a pressure reducing device andis also in communication with the said control valve to be opened andclosed as the latter closes and opens the first-named connection betweenthe manifold and the inlet of the pressure regulating valve.

6. A system as defined in claim 5, in which the said control valve is athree-way solenoid valve.

7. A system as defined in claim 5, in which the pressure reducing devicein the said second connection is a spring loaded check valve.

8-. A system as defined in claim 5, in which the said control valve is atwo-way solenoid valve.

9. A system as defined in claim 5, in which the pressure reducing devicein the said second connection is an outlet pressure regulating valve.

10. A system as defined in claim 1, in which the means for defrostingthe evaporators singly consists of automatically actuated valves adaptedsequentially to open communication between each evaporator and thecommon hot gas defrost conduit.

References Cited UNITED STATES PATENTS 3,150,498 9/1964 Blake 62-510 XRMEYER PERLIN, Primary Examiner US. Cl. X.R. 62278, 510

